This invention relates to an improved, self adjusting release mechanism for use in conjunction with a heavy duty clutch that is equipped with a clutch brake and, in particular, to a release mechanism that is capable of automatically compensating for disc wear without disturbing the axial alignment between the clutch release bearing housing and the clutch brake assembly.
A self adjusting release mechanism suitable for use in a heavy duty clutch is disclosed in U.S. Pat. No. 3,876,049. In this type of clutch, the driven clutch disc or discs are disengaged from between the flywheel of the prime mover and the pressure plate of the clutch by means of a pedal-actuated release mechanism. The pedal is typically connected to the release bearing housing of the clutch through appropriate linkage. When the clutch is in an engaged condition, the driving and driven components are urged into friction engagement by means of pressure springs. As wear occurs on the facing of the clutch disc, the springs force the pressure plate of the clutch closer to the flywheel. Accordingly, greater axial movement of the release bearing housing is normally required in order to achieve clutch braking. Adjustment of the release mechanism, due to facing wear, is soon required in order to maintain the pedal linkage within acceptable operating boundaries. As described in the noted patent, this adjustment is sometimes made automatically by means of a pawl and ratchet arrangement which serves to move the release bearing housing away from the flywheel.
Many clutch units are now equipped with a torque limiting brake which is positioned between the release bearing housing and the transmission. Depressing the clutch pedal to a first position moves the housing, and thus the release mechanism, back a sufficient distance to release the clutch. The released drive shaft, however, continues to rotate at a relatively high speed due to inertia. As described in U.S. Pat. No. 4,046,237, depressing the clutch pedal beyond the initial release position moves the release bearing housing back into friction engagement with the clutch brake unit resulting in the shaft being brought to a controlled stop. As can be seen, in this type of clutch arrangement axial movement of the release bearing housing provides for the release of the clutch as well as the braking of the drive shaft. In order to compensate for disc wear while at the same time retaining continued operation of the clutch, the release housing must be continually repositioned in the assembly.